POS1512 THROMBOCYTOPENIA AND IMPAIRED KIDNEY FUNCTION ARE MAJOR RISK FACTORS FOR RECURRENT THROMBOSIS IN PATIENTS WITH ANTIPHOSPHOLIPID SYNDROME
Authors: N. Karandyszowska, H. Alagündüz, J. Widaeus, F. Carlens, A. Warnqvist, M. Magnussion, I. Gunnarsson, E. Svenungsson, M. Bruzelius, A. Antovic
Journal: Annals of the Rheumatic Diseases (2023)

<h3>Background</h3> Recurrent thrombosis in patients with antiphospholipid syndrome (APS) is a major clinical concern and treatment challenge. Data regarding risk factors and markers of recurrent thrombosis in APS patients, particularly during long-term follow-up, is limited. <h3>Objectives</h3> We aimed to study the effect of cardiovascular (CV) risk factors and antiphospholipid antibody (aPL) profiles on recurrent thrombosis in APS. We continued to explore if the occurrence of thrombocytopenia and decline in kidney function over time could be considered risk factors. <h3>Methods</h3> This retrospective cohort study comprises all patients identified with APS in the electronic medical records at Karolinska University Hospital, Sweden 2014-2020. The patients were followed until death, last medical visit, and thrombotic event. Cox proportional-hazard model was used to estimate hazard ratios (HR) and 95% confidence intervals (95% CI) between groups. A time-varying model was applied when the effect of the occurrence of thrombocytopenia and decline in renal function and time to recurrent thrombosis were assessed. Ethical approval was obtained from the Swedish Ethical Review Authority. <h3>Results</h3> 263 patients were included in the cohort and 52.1% of patients had primary APS. The median age at inclusion was 45 years (35–60) and 66% were women. During follow-up, 47 re-thrombotic events occurred; 29 arterial and 18 venous events, with an incidence of 4.1 per 100 person-years (95% CI: 3 – 5.3). A significant CV risk factor for re-thrombosis was current smoking; hazard ratio 3.62 (95% CI: 1.4 – 9.2). Twenty-two patients (64.7%) with re-thrombosis were triple positive for aPL compared to 99 (43.2 %) without any event at follow-up (p &lt;0.01). There was no difference in the number of patients with re-thrombosis between the primary and secondary APS. The time-varying Cox regression analyses revealed chronic kidney disease (eGFR&lt;60) and thrombocytopenia (platelet count &lt;100x10<sup>9</sup>) hazard ratios 2.41, (95% CI: 1.2 – 5.0) and 7.60 (95% CI: 1.9 – 30.1), respectively, as the major risk factors for re-thrombosis in this cohort of APS patients. The cumulative mortality incidence was 4.5% (n=12). The most common cause of death was sepsis due to bacterial infection at a median age of 63 (IQR 51-71). <h3>Conclusion</h3> Our results demonstrate that the decline of kidney function and the occurrence of thrombocytopenia in APS patients over time are major risk factors for recurrent thrombosis. Adequate surveillance and treatment options are necessary to improve kidney function and thrombocytopenia and thereby prevent further morbidity in APS patients. <h3>REFERENCES:</h3> NIL. <h3>Acknowledgements:</h3> NIL. <h3>Disclosure of Interests</h3> Natali Karandyszowska: None declared, Hevgin Alagündüz: None declared, Jacob Widaeus: None declared, Felicia Carlens: None declared, Anna Warnqvist: None declared, Maria Magnussion: None declared, Iva Gunnarsson: None declared, Elisabet Svenungsson Shareholder of: AstraZeneca and Pfizer, Speakers bureau: Janssen, Grant/research support from: Grant support from Merck, Maria Bruzelius: None declared, Aleksandra Antovic: None declared.